One common method used in the electronics industry to manufacture LED display devices is to provide first and second bus conductors on a ceramic substrate with the first bus conductors extending normally of the second bus conductors. The LED's are mounted on the ceramic substrate with each LED located between, or adjacent to, two parallel first bus conductors and adjacent to, or between, two parallel second bus conductors. The bus conductors are connected to the LED's by extremely fine wires which are bonded to the bus conductors and to the LED's. The bus conductors are connected to suitable driver circuits which supply the signals for energizing the LED's.
The presently known manufacturing methods, such as the one described above for producing panel displays, result in relatively high production costs since the conductors must be provided on a ceramic substrate, the LED's must be bonded or otherwise secured to the substrate in some way, and numerous wire bonding operations must be carried out to connect each LED to one of the first bus conductors and to one of the second bus conductors. The present invention is, in accordance with one aspect thereof, directed to the achievement of an LED panel which can be produced at lower cost than is possible by presently known manufacturing methods.
In accordance with a further aspect of the invention, a light collimating means is provided for each LED in a panel. An individual LED produces only a minor amount of illumination and the light emitted is radiated in all directions from an energized LED. The viewer positioned in front of a LED panel, therefore, sees only a portion of the relatively minor amount of illumination produced by an individual LED. Furthermore, when information is displayed, an individual LED may be energized for only an extremely short time interval, a fact which further limits the usefulness of LED display panels. A light collimating means in accordance with the present invention has the effect of focusing the light emanating from individual LED's directly towards the viewer, and enhancing the clarity of the display.
In accordance with the present invention, a flat panel display device is manufactured by providing a thin flexible insulating film with the first and second bus conductors on the oppositely facing surfaces thereof. The first bus conductors extend parallel to each other and are arranged in rows while the second bus conductors are arranged in parallel columns which extend normally of the rows. LED receiving openings are provided between adjacent rows and between adjacent columns. First and second tap conductors extend from the first and second bus conductors to each of the openings, the tap conductors being located on the first surface of the film.
Prior to assembly of the LED's to the film, a grating having cells therein arranged in accordance with the grid pattern of the display is placed against the second surface and secured to the second surface. The individual LED's are then inserted into the openings from the first surface of the film so that portions of each LED are surrounded by the sidewalls of a cell. When the LED's are inserted, portions of the film are flexed in the direction of insertion and the tap conductors are thereby brought into contact with the LED's. The grating serves physically to support the film and the sidewalls of the cells function as reflecting surfaces for the LED's when they are energized.